Method of seasoning wood



Patented Oct. 8, 1940 METHOD OFSEASONING WOOD James R. Helson, Metropolis, Ill.

No Drawing.

8 Claims.

This invention relates to-patent-class of woodpreserving, 'andrespecially to an-improved method for seasoningwood for impregnating purposes. To avoid confusion in the use of the words tim- I bers (timber)., lumber, and wood it "should be understood that the invention is applicable to logs, poles, ties, sawed or hewed beams, chunks, boards; stripsror shingles of wood; and while it is not needed for firewood, the term ffwood is chosen as the'broad or inclusive word tobe hereinafter used'to cover the fieldof usefulness-of the invention, 'whether the wood be quite green-or partially seasoned.

*One object .of the invention is to provide a method and means for seasoning wood-much more quickly:- and uniformly than has heretofore beenzaccomplished without cracking or checking the Wood. Y L

Another objectis to provide a method for utilizing a fi.reretardent solution as a medium of. seasoning wood.-,

Another object is to provide a method for utilizing timber-preservatives or decay-retardents in liquid state as a medium, of seasoning wood.

- Another objectis to provide a method for utilizing-liquids .or fluids-as a medium of transmitting heat in this method of seasoning wood.

Another. object is to provides. method whereby wood can be seasoned. uniformly 'from the exterior surfaces to the innermost parts of the wood, even when the wood is in large and thick pieces.

Another object is to provide a method whereby any desired part of the moisture in wood'can be removed uniformly from the exterior and interior alike without detriment tothe wood.

Another object is to provide a method whereby the amount of moisture removed from the wood can be ascertained to facilitate knowledge as to what degree the wood is seasoned.

Another object is to provide a method'for seasoning wood uniformly and to the desired extent, so that it 'can be impregnated with liquid (oil, tar or solution) preservative or fire-retardent. 45 Another object is to provide a method whereby wood preserving or other apparatus can be used and steps can be carried out by the alternative or successive application of pressure and vacuum in connection with the application of hot liquid in which the wood is immersed.

Before describing the method, it may be well to mention, in detail, some of the numerous fireretardents and decay-retardents that may beemployed in this method for seasoning woods of Application March 30, 1934, Serial N0. 718,205

various kinds and in various stages from green to partially seasoned:

Among the decay-retardents are:

Creosote or creosote oil,

Coal-tar or coke-oven-tar,

Water-gas-tar,

Crude petroleum or derivatives therefrom, Mixture or solution of two or more of these.

Among the decay and .fire-retardents, one or the other, or both are:

Zinc-chloride, 1 Mercuric chloride,

, Sodium-fluoride, xArsenic,

, Borax,

Salts of various kinds.

. For utilizing these or other preservatives in this method, they must be in liquid form, that is, the tars-must be melted, and the salts must be in solution; but the seasoning (without preserving) may be effected by the use of pure water or other liquid, so the term liquid" will hereinafter be used as broadly stating any liquid or fluid that is applicable in the method and capable of producing the desired result in presence of suflicient heat and pressure, and followed by vacuum, in the manner presently described. The term liquid also includes mixtures of these respective fire-retardents and decay-retardents, or with others not herein mentioned.

It is generally conceded by wood preservers that 260 degrees Fahrenheit temperature, or slightly more than 20 pounds steam pressure, is not injurious to any of the treatable woods, while some can stand 2'74 degrees F., or 30 pounds pressure.

The standard practice of steaming wood over long periods to heat it for artificial seasoning so that it can be impregnated, saturates the wood to maximum absorption, thus leaving a great deal of moisture in the wood when all heat is dissipated after releasing the steam pressure and creating vacuum.

In my method, no moisture is added to the wood when using oils or tars as the transmitter of heat, and air pressure is first used to fill the pores of the wood for retarding absorption, whereupon aqueous solutions are used as the transmitter of heat.

The theory of my method is to store heat units in the moisture-containing wood held under surrounding pressure, next to dissipate the heat units as latent heat, in the volatilization of moisture by releasing the said pressure, and immediately thereafter to create a vacuum around the wood.

In a simple and broad sense, the invention consists in the following steps: 1) Immersing or submerging moisture-containing wood in an appropriate liquid, (2) applying sufficient heat and pressure to the liquid to thoroughly heat the wood to a suiiiciently high temperature to volatilize a considerable part of the moisture within the wood when released to normal .or atmospheric pressure, (3) separating the submerging liquid from the wood, and (4) subjecting the thoroughly heated wood to surrounding air that is sufficiently rarifled to volatilize the remaining moisture-of the wood, so as to season the wood uniformly throughout and to facilitate knowledge as to what degree the wood is seasoned, the moisture volatilized from the wood can be condensed and measured.

The above defined simple method is economically and conveniently eifec'ted in apparatus commonly used for pressure treatment of timber, consisting of a retort in combination with mechanical means to introduce the submerging liquid, to .apply pressure thereto, to apply heat thereto, to compress air within the retort, to rarify the air therein, and to condense the moisture volatilized therein.

When wood is partially seasoned, or when at any time it is desirable to retard absorption, by the wood, of the heating liquid, initial air pressure should be applied to the wood within the retort, thus filling the pores of the wood with compressed air, and as the liquid is introduced, the surplus air is released at a retarded rate to maintain the desired pressure around and within the wood. When the retort is filled with the liquid, it is sealed to maintain the desired pressure, and heat is applied to the liquid through steam coils or other appropriate means and thus, through the heating period, both temperature and pressure are maintained at desired predetermined degrees until the timber is heated throughout to a temperature sufiiciently high to volatilize a desired part of the moisture in the wood when the pressure is released. After the submerging liquid is removed from the retort, generated steam is allowed to pass off, thus dissipating all temperature in excess of 212 degrees Fahrenheit. By means of any appropriate apparatus, vacuum is next created and maintained in the retort over the wood and liquid, and as the moisture in the wood is volatilized, more heat is dissipated as vacuum is increased by operation of said apparatus, thus lowering the boiling point more and more until when 24 inches of vacuum is recorded, whereat water boils at 40.6 degrees F.; so, at 26 inch vacuum the moisture is volatilized at 125.4 degrees F.; at 27 inch vacuum, at 115 degrees F.; and at 28 inch vacuum, at degrees F.

Inthe manner explained above, the heat stored up in the wood, during the heating period or step, is used in volatilizing the moisture therein when pressure is released and vacuum is created, thus seasoning the interior and exterior of each piece of timber or wood in direct proportion to the amount of heat stored and dissipated.

It is essential to maintain and control suflicient pressure around the wood to prevent volatilize.- tion of moisture therein during the heating period and until the timber is thoroughly heated to and through its center, as lack of pressure would not only allow dissipation of heat, but also allow removal of moisture from exterior surfaces of the wood before its center is heated, which in turn would cause checks and cracks in the exterior surfaces in consequence of shrinkage being greater at the exterior than at the interior or center.

I accomplish the desired results in this method by operation as follows:

Starting either with or without initial air pressure in the retort in which the wood is being seasoned, the wood is submerged in liquid and the submerging liquid is heated toa predetermined temperature with pressure maintained suflicient to prevent moisture from volatilizing for a predetermined period, according to the kind of wood, the size of the pieces, and the moisture content of the wood. Next, separate the liquid from the wood and release the pressure, thus letting stored heat in the wood in excess of boiling temperature at atmospheric pressure be dissipated by volatilizing moisture from the wood, which moisture passes oil as vapor and can be condensed if desired. Next create and maintain vacuum over the moisture-containing wood within the retort and thereby dissipate as much of the remaining stored heat as is possible or desirable by volatilization of moisture in the wood through low boiling temperatures of vacuum.

By the above described method, the center and surface of the wood are simultaneously seasoned, that is, the wood is seasoned uniformly throughout and is susceptible to impregnation with fluid preservatives, in volume as great as, or greater than that of the moisture extracted, and preservative fluid can be distributed to. the innermost parts of the wood from whence the moisture was volatilized.

I have no intention to limit my patent protection to the precise details given in the foregoing, for the invention is susceptible of numerous changes within thescope of the inventive ideas herein implied and claimed.

What I claim as my invention is:

1. The wood-seasoning method which includes submerging moisture-containing wood in suitable liquid under adequate pressure initially to prevent volatilization, applying and maintaining sufiicient heat to the liquid to thoroughly heat the wood throughout to a sufliciently high temperature to volatilize a considerable or desired part of the moisture in the wood when in atmospheric presure and separated from the submerging liquid, and thereafter subjecting the wood to surrounding air which is continually kept sufficiently rarifled below normal atmospheric pressure to volatilize a desired or substantial part of the moisture in the wood.

2. The wood-seasoning method which includes submerging moisture-containing wood in suitable liquid under adequate pressure initially to prevent volatilization, applying and maintaining suflicient heat to the liquid to thoroughly heat the wood throughout to a suficiently high temperature to volatilize some of the moisture of the wood when separated from the submerging liquid and allowed to stand at atmospheric pressure, and thereafter subjecting the still-hot wood to surrounding air which is continually kept sufliciently rarifled to volatilize a considerable or desired part of the moisture remaining in the wood.

8. The wood-seasoning method which includes submerging moisture-containing wood in a suitable liquid under adequate pressure initially to prevent volatilization, applying heat to the liquid without applying pressure other than that of heat-expansion, maintaining the heat at a sufficiently high temperature to thoroughly heat the wood throughout sufliciently to volatilize moisture and liquid in the wood when the pressure is reduced to atmospheric pressure, separating the submerging liquid from the wood, and thereafter subjecting the thoroughly heated wood to surrounding air that is continually kept rarifie'd bea sufliciently high temperature to volatilize a or substantially all of the remaining moisture in the wood is volatilized.

5. The wood-seasoning method which includes impregnating moisture-containing wood with compressed air, submerging the air-impregnated wood in a suitable liquid under slightly greater pressure than that of the initial compressed air and thereby driving part of the liquid into the wood to sufficient depth to increase compression of the compressed air in the pores of the wood and thereby intensifying the heat, applying heat to the liquid besides the heat of compression, and

maintaining the heat at a sufilciently high temperature to volatilize moisture and liquid in the wood when the pressure is reduced to atmospheric pressure, separating the submerging. liquid from the wood, releasing the pressure for permitting the compressed air in the wood to force out some of the liquid which has entered the outer'surfaces, and thereafter subjecting the air-impregnated and thoroughly heated wood to surrounding air sufficiently rarified below normal atmospheric pressure to volatilize the desired part or substantially all of the remaining moisture and liquid in the wood.

6. The method of seasoning wood and impregnating the outer surface of the wood with woodpreserving material, which method comprises submerging the wood in a volatile liquid which includes or constitutes the wood preserving material, applying sufiicient pressure to the liquid to prevent initial volatilization, applying sufficient heat to the liquid to thoroughly heat the wood throughout to sufliciently high temperature to volatilize part of the moisture at atmospheric pressure, after separating the submerging liquid from the wood, and thereafter subjecting the heated and partially impregnated wood to, surrounding air that is continually kept sufliciently rarified to volatilize aconsiderable part of the volatile constituent of the liquid and a desired part of the moisture in the wood and to leave a part of the non-volatile constituent within the wood for preserving the wood;

7. The herein described wood-seasoning method which comprises partial or slight impregnation of woodwith liquid which includes volatile'and non-volatile constituents which arecombined to form a wood preservative, applying to the partially or slightly impregnated wood a sufiicient of the volatile constituent when the pressure is reduced to normal atmospheric pressure, separating-the wood from the submerging liquid, and subjecting the hot wood to surrounding air which is continually kept suificiently rarified a sufficient time to volatilize approximately all of the remaining volatile constituent and moisture. in the wood, leaving the non-volatile constituent precipitated in the wood as a preservative.

8. The herein described method of seasoning green or semigreen wood for impregnating purposes, using hot preservative liquids in contact with the wood as the medium of transmitting heat to the wood; which method includes applying compressed air in the pores of the wood to retard the absorption of the liquid during the heating period, submerging the air-impregnated wood with the heating liquid, applying heat to the liquid and applying force to the liquid to subject it to pressure to maintain the compressed air in the pores of the wood and to intensify the heat and for avoidingdissipation of heat through volatilization during the heating period, discharging the heating liquid from around the wood,

maintaining air pressure on the wood while the liquid is being discharged, reducing air pressure to normal atmospheric pressure andthus discharging air and liquid and volatilized moisture from the wood by the air pressure in the pores 

